Fix indentation of an if-else
Don't prompt on gnus exit
Reset to default sorting for gnus threads
Hide gnus summary subthreads by default
Set gnus variables in one place
Clean up gnus locations

- Don't hardcode gnus locations.
- Remove locations that are unused or that are already their default
  values.
Revert gnus theads sorting to most recent number
Revert "Disable vc for git"

I disabled vc for git in b453a51 because I didn't think I used any
features of vc and didn't see the point of it taking up space on the
mode line. But now I'm missing the option to follow version-controlled
symlinks, so I'm turning it back on.
Always follow vc symlinks